Robert and Arlene Holmes arrive at district court for a hearing in the case of their son, Aurora theater shooting suspect James Holmes, in Centennial, Colo., on Monday. The prosecutor announced he will seek the death penalty against Holmes.

CENTENNIAL, Colo. — Prosecutors on Monday said they will seek the death penalty against the man accused in last year’s movie theater attack that killed 12, injured 70 and spurred new gun control laws in Colorado.

The much-anticipated disclosure came in a court hearing held four days after prosecutors publicly rejected an offer by James Holmes’ attorneys that the former neuroscience graduate student would plead guilty to avoid execution.

Prosecutors had said the defense proposal wasn’t a valid plea bargain offer, although they could still agree to a plea before the case goes to trial.

The decision to seek execution will delay the start of the trial until at least February, and the judge acknowledged even that might not be enough time for all sides to prepare. The trial had been planned to begin in August.

“It’s my determination and my intention that in this case for James Eagan Holmes justice is death,” Arapahoe County District Attorney George Brauchler said at the Monday hearing. He spoke quietly and deliberately without any hesitation.

There was no audible reaction from Holmes, who sat in court with his back to reporters.

Holmes’ parents sat side by side in the gallery, clutching hands with fingers intertwined.

They were also quiet, as were the victims in the courtroom when Brauchler disclosed his decision, which he said he had shared with no one.

He said he had personally discussed the case with 60 people who lost relatives in the shooting. Overall, prosecutors have consulted with 800 victims and relatives.

Bryan Beard, whose best friend Alex Sullivan was killed in the attack, was in an overflow courtroom during the announcement.

“I had a huge adrenaline rush,” he said. “I love the choice, I love it, I love it ... I hope I’m in the room when he dies.”

Holmes’ attorneys are expected to argue he is not guilty because he was legally insane at the time of the July 20 shooting. They balked at entering that plea last month, saying they couldn’t make such a move until prosecutors made a formal decision on the death penalty.

Investigators say Holmes methodically stockpiled weapons and ammunition for his assault on a packed midnight screening of “The Dark Knight Rises” and booby-trapped his apartment to explode and distract any police who responded.

Last week, prosecutors said they had rejected an offer from Holmes’ attorney to have him plead guilty and serve life in prison, saying the offer wasn’t a serious attempt at plea bargaining. They accused the defense of trying to gin up public support for a plea deal.

In a sign of how long the case could drag on, District Judge William Sylvester on Monday named a new judge — Carlos A. Samour Jr. — to take over the case. As chief judge for the district, Sylvester is responsible for the overall running of the court. He said he couldn’t do that and oversee a complicated death penalty case.

In his order, Sylvester said “a final resolution of this case is now likely years away.”

The timeline disturbed victims.

“It could be 10 or 15 years before he’s executed,” said Pierce O’Farrill, who was shot three times in the attack. “I would be in my 40s, and I’m planning to have a family, and the thought of having to look back and reliving everything at that point in my life, it would be difficult.”

Prosecutors said they want the case wrapped up by spring of next year. But defense lawyers objected, saying the trial alone would take at least nine months and can’t even start until numerous pretrial issues are resolved.

“They are trying to execute our client, and we will do whatever it takes to defend his life,” said Tamara Brady, an attorney for Holmes.

The judge tried to strike a compromise with a trial starting on Feb. 3 and ending in June but acknowledged that schedule might have to be pushed back.

Prosecutors could eventually accept a plea deal but would want to ensure that it’s air-tight, said Karen Steinhauser, a former prosecutor who is now an adjunct professor at the University of Denver law school.

Holmes would give up his right to appeal by pleading guilty, she said. He could ask to change a plea if new evidence surfaced or he claimed his lawyers were ineffective, but “it’s very, very hard to withdraw it,” Steinhauser said.

In addition, the judge would want assurances from defense lawyers that Holmes is mentally competent to plead guilty and accept a life sentence with no parole, Steinhauser said.

The judge could order a mental competency evaluation before accepting a guilty plea, but Steinhauser said that’s unlikely unless Holmes showed some sign of incompetence.

The theater massacre was repeatedly cited by gun control advocates who pushed a hotly contested package through the Colorado Legislature last month. The bills include a ban on the sort of high-capacity magazines used to spray the theater with dozens of bullets in a matter of seconds.

President Obama is scheduled to visit Denver on Wednesday to highlight the legislation as part of his push for more gun control following December’s Sandy Hook Elementary School massacre.